GLEAM for DMWG

Eduardo do Couto e Silva

Oct 23 , 2002

SLAC

Main objective

Develop a likelihood program to search for photons from neutralino annihilations

using the new GLEAM Monte Carlo.

This work leverages on the development of the data analysis infrastructure for LAT I&T maintained by Xin Chen, who was kind enough to provide us with his

“nuggets of wisdom”

Shopping list… Source flux for different MSSM models (e.g DarkSUSY). – See A. Morselli’s talk. Background flux (e.g EGRET parametrization used in Bergstrom et al Astr. Phys 9 (1998), 137.)

Orbit model for GLAST – See T. Burnett’s talk.

Energy resolution – See CAL group report in LAT IDT meeting

PSF – See W. Atwood’s report in LAT IDT meeting

Likelihood program

The approach

Develop a simple likelihood program and interfaces the main ingredients described in the previous page

Develop software infrastructure for systematic studies

Implement a more sophisticated likelihood approach to maximize our sensitivity based on details of the LAT design.

Signal and Background

2

2

2

)(

2

1

sEE

s e(i)L

)(iE

a(i)bg L

Likelihood of event i to be a neutralino signal

Likelihood of event i to be a background

we assume . Es

(To be replaced by measured spectrum from GLEAM with including orbital effects and appropriate

normalizations from DarkSUSY)

N

isbg

ssbgbgN

sbgNN

NN

iNiN

N

NNe sbg

1

)()(

!

LLL

Fit parameters

Nbg = number of expected background events

Ns = number of expected photons

= power law coefficient

Es = neutralino energy

Extended Likelihood

2.2 2.4 2.6 2.7

Nb 1156 554 269 188

An example of Fitted Parameters

Input value = 60

Input value = 50

Input value = 1156 Input value = 2.2

LAT sensitivity

Each point corresponds to 1000 MC experimentsAnd assumes a 5 sigma detection threshold

E/E

Summary

We have developed a simple likelihood code and some infrastructure to run GLEAMWe have started to run GLEAM with the orbit corrections (not presented in this talk)We are eager to work with the v3 release of GLEAM